Abstract: Reservoir Characteristics of the Tarim Basin, China

Song Cao, Jie Tang

The reservoir rocks in the Tarim Basin, China, can be divided into two major groups, separated by an unconformity at the base of Silurian. The reservoir rocks below the unconformity are dominated by carbonates of upper most Precambrian, Cambrian, and Ordovician. The average porosity of these rocks is about 1-4%. The pore space is mainly secondary and dominated by voids, carverns, and fractures. The porosity can reach as high as 24% within the weathering zones in some areas. These weathering zones which were developed due to erosion have played an important role in hydrocarbon accumulation in the basin. The reservoir rocks above the unconformity are dominated by clastics of Carboniferous, Triassic, Jurassic, Cretaceous, and Tertiary. The reservoir quality of these reservoir rocks is co trolled in large by the depositional environment. For example, Carboniferous reservoir rocks have an average porosity of 18% for shoreface beach sandstone and an average porosity of 12% for tidal flat sandstone. The Mesozoic and Cenozoic reservoir rocks are superior to the Paleozoic reservoir rocks in reservoir quality with higher porosity and permeability. For example, the Cretaceous sandstone in Yimaili area has an average porosity of 22% at depth of 4,900 m. In general, the clastic reservoir rocks have better reservoir quality than carbonate reservoir rocks.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994